Six colors, one national standard, and a seventh that means something different from all the rest.
Walk any active job site in the metro and you will see paint and flags in a specific set of colors. They are not decorative and they are not arbitrary — they follow the American Public Works Association uniform color code, used nationwide.
## The code
**Red** marks electric power lines, cables, conduit and lighting cables.
**Yellow** marks gas, oil, steam, petroleum and other gaseous or flammable material. In Colorado this is the one to treat with the most caution: natural gas accounted for 44% of all facility damages in 2024.
**Orange** marks communications — telephone, cable television, alarm and signal lines, and fiber conduit.
**Blue** marks potable water.
**Green** marks sewers and drain lines.
**Purple** marks reclaimed water, irrigation and slurry lines.
**Pink** marks temporary survey markings — not a facility at all.
**White** is the odd one out. White does not mark anything buried. White marks *proposed excavation* — the area you intend to dig, marked by you, before the locators arrive.
## Why white matters most
Of all seven colors, white is the one excavators control, and it is the one most often skipped. White lining tells the locator exactly where to focus. Without it, they are working from a text description of your dig area, and the gap between what you wrote on the ticket and what you meant is where unmarked facilities live.
## Marks are not permanent
Paint fades. Flags get pulled by weather, traffic and the public. Colorado tickets have a defined life, and if marks become illegible or the work extends past the ticket, you need to request a re-mark rather than working from memory of where the lines used to be.
And when you do have marks: respect the tolerance zone. Hand-dig or use vacuum excavation within it. The marks tell you a facility is present in the vicinity — they do not promise the precise centerline down to the inch.
- locating
- APWA
- homeowners